Whats to say that speed gun is off? I know of this speed gun that was used for my plane along with numerous others that have used it at SEFF and other fly-ins we have at Mac's. All the speeds are pretty much dead nuts on whether its a pylon racer or big bird. Not to mention people like Bob Violet etc...being clocked with this same gun and agreeing with the speeds. I know in a straight line I can pedal a bike probably to 20mph but coming down a hill and pedaling I could probably hit 35 or 40mph with the same gear ratio. We could probably go around and around about how speed is calculated and whichever math, dopler or gun is inaccurate. I know I've flown planes around 160-180mph and I do know for a fact my Viper that I flew last weekend was a ton faster than what I have ever flown. I've never had to be ahead of a plane before and to keep up with it at speed from a dive and in front of me maybe 20ft off the ground I had to be way ahead of it.

OK, fair enough , but what you are saying is, if a Viper can go 217mph in a dive. how fast would it be with 5s ? 230mph ? and we can go on, put in a higher kv motor and go 5-6 s, how fast ? 250mph, or a bigger prop, 260mph ?

You see where its going.. If all this where true then you would hold the world record just by adding 1 or 2 cell lipo in your plane, we all can agree that this is not the case, so where is the fault ? I dont know, I really dont, you say the speedgun is accurate, ok, I can buy that, but still, I just cant believe it goes 217mph even in a big dive with a mild 4s setup,,,,, if this would be true, then everyone could buy a Neu 1115 1Y and put in a pylon, and go 200mph with 3s and 217mph with 4s wihout even pushing the motor... again, this is not true, you need at least +2000w static to go thoses speeds you are getting, at least, maybee more like 2500 watts..

Please dont get me wrong here, I have a Viper, and would be very glad if this was true, as I have a Mega 16/40/1 to put in mine, my thoughts was 5s, reaaly overkill, but if what you are saying is true, well then I can stick with 4s on that motor and get 225 mph in a dive ,, the only problem, it aint going to happen !

So If your Neu motor isnt some new technology secret, then Im sorry, something if off...

The fastest Viper Ive seen thats been clocked is 356km/h, and he was flying a lehner motor with 5s lipos abd a 5.2x5.2 prop, you are still pretty far away from that power...... ... so tell me, how can you with 1200 watts of power fly as fast as other who have Vipers at +2000 watts ? I cant get it ?

Other then that, great flying man, you sure know how to make those low passes, put in 5s now, and try again, now you are getting close to the real speeds, but you would need 6s to be up front ..

If the prop could take 6s wothout getting the tips over soundbarrier, and stay within efficency, I would believe +217mph...

I'm pretty sure it's a given and readily accepted that the 5S setup I'm using (Neu 1115/2.5D - 2100kV, 5S batteries, 5.25 x 6.25 prop, 1700W static, 1100W airborne) is good for about 200mph, so I'd be a little surprised myself if a 4S setup with a smaller prop would go much more than that.

I don't speak from any imperical data, just from intuition and what I've learned/read from this thread. I don't think guys are getting much more than 200mph on the Viper (or, I'm all washed up which is certainly possible!).

Ok, what we done yesterday and for information purposes only. We installed an eagle tree airspeed system on a Fun Jet. After the altitude correction factor was added after landing, it gave us a speed of 154 mph. These were done without dives and were crosswind. Also, we downloaded and installed the RCSpeedo app on an android cell phone. This app gave us a crosswind speed of the same Fun Jet of 153.5 mph at the same time as the Eagle tree system.
So, they were very close when used together. Then we downloaded this Vipers youtube video and ran it on rcspeedo on a PC when we got home. It gave us a speed of......208 mph.
So, maybe this big dive, which he does state was done, does pick up more speed than one realizes. It should when one thinks how slick the viper is IMHO.
Me thinks also, straight and level, with the power setup on this Viper, would see 180's plus.
Just some additional thoughts and what we saw yesterday.
Oh, we did use the rcspeedo app on another Fun Jet, same motor and prop, only difference were the battery's. 0ne was a 25C and the other was a 45C. The rcspeedo did show a difference of about 10 mph. 153.5 V 144 mph. When we put the 45C into the slower Fun Jet, it picks up the same speed as the other.

And as always, I am trying to discuss this matter, Im not saying you are lying or cheating, or that the speedgun is bad, Im just trying to understand this !!!

And if its true, well I would be VERY happy, but confused !!!

Oh I'm not thinking anything like that. I just look at it this way and make examples to myself and normally my examples kinda work. LOL I understand about motor, prop and power. I agree there. But the one thing I keep thinking and using this scenario. Ok you take a 10 speed bike and get on it in 5th gear and pedal as fast as you can. The bike (the plane), you (the motor) and the gears (esc or torque LOL) On a straight road with no incline we will say you can pedal it at 20mph. After a little rest, cause I would be tired, LOL, you take the bike on a 45 degree incline or more and stay in the same gear and pedal just as hard. Now you havent gotten stronger, the gear hasnt changed, your weight hasnt increased but more than likely you will be able to increase that speed not by a little but I'm quite sure by a big amount. I look at it the same way with the plane. Its not making any more power but the rpm's are probably going up a little now because gravity is pushing down the plane increasing your overall speed. Hopefully I havent confused anyone but with any kind of incline you will increase speed by a good bit. I just think that these planes are going a lot faster than what some folks are giving credit to. I could be wrong.

Ok, what we done yesterday and for information purposes only. We installed an eagle tree airspeed system on a Fun Jet. After the altitude correction factor was added after landing, it gave us a speed of 154 mph. These were done without dives and were crosswind. Also, we downloaded and installed the RCSpeedo app on an android cell phone. This app gave us a crosswind speed of the same Fun Jet of 153.5 mph at the same time as the Eagle tree system.
So, they were very close when used together. Then we downloaded this Vipers youtube video and ran it on rcspeedo on a PC when we got home. It gave us a speed of......208 mph.
So, maybe this big dive, which he does state was done, does pick up more speed than one realizes. It should when one thinks how slick the viper is IMHO.
Me thinks also, straight and level, with the power setup on this Viper, would see 180's plus.
Just some additional thoughts and what we saw yesterday.
Oh, we did use the rcspeedo app on another Fun Jet, same motor and prop, only difference were the battery's. 0ne was a 25C and the other was a 45C. The rcspeedo did show a difference of about 10 mph. 153.5 V 144 mph. When we put the 45C into the slower Fun Jet, it picks up the same speed as the other.

Regards, Tom.

So maybe the speed is coming out. Sounds like a fair comparison and test that you guys did. I dont think I'm going 200mph in straight and level. Like you said maybe 180's. But I do know I did see a huge and noticeable difference in speed from a dive. Not only by the sound but how much faster I had to turn my head when it came by me. LOL

Tom, first of all, I have done tons of doppler for me and a bunch of Swedish forum members,,,, and IF flyed correctly as if the pilot knows its doopler time, you should fly straight over and hold you throttle, you cant put a big dive and then straight out just before, as the plane dives the dopller pick up the higher frequency more then it should, so this would give a higher speed then the real.. This is really hard to put a finger on and say you have to do it this way,,, I can get 133mph in my 5s funjet, straight and level, but I can also get 142mph just by diving before and then straight out level long before.. BUT if I dive and straight out just before the camera, i get 158mph, so this gives me 158/133 more gain, which is a 19% gain in speed, take it backwards from there, 217mph - 19% = 176mph, and BINGO!! it is the real speed..

there was a speedgun involved which "can" show a slight fragment of speed in the last fraction of seconds in the end of the dive, which "could" possible be +200mph, or even the 217mph claimed.... I dont have all the answers, but I do know if that Viper with 4s and the 1115 1Y with the apc 4.75x4.75 prop flyes dead level on a calm day without any wind, it will not get past 180mph...

I can get my turn left pylon go 220mph with a 3s lipo and 600 watts, how?, put led at CG to make the plane really heavy,,and take my time to get 2000 feet high, and do a big dive, full power, then I would probably get fantastic speeds no matter if doppler or speedgun...but what does this say me, that a falling object can reach high speeds, yes I know,,,,, the only speed that we can measure against other is flat and level a calm day, or fly in both directions level and do the math,,, there are only 3 ways to measure speed correct in my opinion, with an accurate calibrated pitot tube, dopller correct performed or like the german guys do in their speed cup, measure up a distance, and then pure mathematics.... the last is hard to do and costs much.... so Doppler will be fine..

And its up to each one to dive, or not, tailwind or not..... in the end I think we all know what is a relaiable speed or not achieved by someone, I dont think its easy to fool in a high speed forum, there are to much clever people here knowing to much, (not saying Im the one of them )

Also, we would like to add, we noticed the airplane windsock at the start and end of your viper video. It shows an increase in wind speed which could of been caused by several things. One, being a passing thermal. If you unknowingly dove in this passing thermal, that really could of increased your gound speed which the radar gun might have picked up on.
So, then that 217 mph, now comes into a clearer picture. But we need to remember, that Viper sure sounds good and that motor really is pumping out some rpm's for sure.
Good flying for a maiden............

Its not making any more power but the rpm's are probably going up a little now because gravity is pushing down the plane increasing your overall speed. . I could be wrong.

A little yes, but not more then 20%, look at graphs from other who have inflight data, and about the same setup as yours, they dont get 39K rpm in levelflight and the +47K rpm in a dive after a few seconds...

Also, we would like to add, we noticed the airplane windsock at the start and end of your viper video. It shows an increase in wind speed which could of been caused by several things. One, being a passing thermal. If you unknowingly dove in this passing thermal, that really could of increased your gound speed which the radar gun might have picked up on.
So, then that 217 mph, now comes into a clearer picture. But we need to remember, that Viper sure sounds good and that motor really is pumping out some rpm's for sure.
Good flying for a maiden............

Regards, Tom.

Could be...

As I said, i am NOT saying the speedgun is showing wrong, but a big dive with tailwind and even passing thermal can make wunders maybee ? I dont know cause thats not the way speed should be measured.... you only foll your self, but of course, you get that "swoooosch" feeling whe it passes you, but its still a 180mph setup... and the guys deside him with same setup only he exchanged the motor to a mega 16/40/1 will het even faster "SWOOOOOOOSCHHHES"m but still he only have a 190mph plane straight and level,,, to add it a bit more, put weight inside, then you get even more speed..

We have to take things apart, is it real speed we want to know, or something other ?

speed to me is a given distance divided by time, and the distance cant be to small, or else I can get a hotliner in some moments to show 300mph with the "wrong" way to measure, even if it only goes 150mph.. sudden change in small time cant counter..

Tom, first of all, I have done tons of doppler for me and a bunch of Swedish forum members,,,, and IF flyed correctly as if the pilot knows its doopler time, you should fly straight over and hold you throttle, you cant put a big dive and then straight out just before, as the plane dives the dopller pick up the higher frequency more then it should, so this would give a higher speed then the real.. This is really hard to put a finger on and say you have to do it this way,,, I can get 133mph in my 5s funjet, straight and level, but I can also get 142mph just by diving before and then straight out level long before.. BUT if I dive and straight out just before the camera, i get 158mph, so this gives me 158/133 more gain, which is a 19% gain in speed, take it backwards from there, 217mph - 19% = 176mph, and BINGO!! it is the real speed..

there was a speedgun involved which "can" show a slight fragment of speed in the last fraction of seconds in the end of the dive, which "could" possible be +200mph, or even the 217mph claimed.... I dont have all the answers, but I do know if that Viper with 4s and the 1115 1Y with the apc 4.75x4.75 prop flyes dead level on a calm day without any wind, it will not get past 180mph...

I can get my turn left pylon go 220mph with a 3s lipo and 600 watts, how?, put led at CG to make the plane really heavy,,and take my time to get 2000 feet high, and do a big dive, full power, then I would probably get fantastic speeds no matter if doppler or speedgun...but what does this say me, that a falling object can reach high speeds, yes I know,,,,, the only speed that we can measure against other is flat and level a calm day, or fly in both directions level and do the math,,, there are only 3 ways to measure speed correct in my opinion, with an accurate calibrated pitot tube, dopller correct performed or like the german guys do in their speed cup, measure up a distance, and then pure mathematics.... the last is hard to do and costs much.... so Doppler will be fine..

And its up to each one to dive, or not, tailwind or not..... in the end I think we all know what is a relaiable speed or not achieved by someone, I dont think its easy to fool in a high speed forum, there are to much clever people here knowing to much, (not saying Im the one of them )

Sebbe

Sebbe, we agree with you 100 percent. He does state he did dive and from straight and level their was a huge speed difference. So, he is being straight up. Trust me, we ALL know better than to pull the wool over your eyes! Just sharing what we got when we flew yesterday. This just happened and really wasn't planned!

Maybe what we need is a new speed catagory. Highest Vertical Speed attainded followed by the loudest crack during pull out wins!! Now, this will attract attention from everywhere!! I'll go last and reserve my choice of withdrawing.

Yeah all I'm claiming is a 217mph max speed from a dive and then leveling off and passing by. I don tthink I'm near that straight and level. Dont get me wrong, it is hauling azz straight and level but I dont think its 200mph. LOL